1. Field of the Invention
The invention is directed to an improved valve for controlling fluids, and more particularly to such a valve which may be used in a fuel injection system.
2. Description of the Prior Art
One valve known from German Patent Disclosure DE 101 40 529 A1 can be used for instance in a fuel injection valve, in particular in a common rail injector of a diesel internal combustion engine of a motor vehicle.
The valve known from DE 101 40 529 A1 includes a piezoelectric actuator unit, which has an actuator base and an actuator head. The actuator base is braced, via a rounded, annular edge, on a conical seat that is embodied on a valve housing. The actuator head acts on a coupling module, which includes a so-called adjusting piston which is connected to the actuator head and is operatively connected to a so-called actuating piston via a hydraulic coupler. The actuating piston acts on a valve closing member, which cooperates with a valve seat and by means of which a stream of fluid can be controlled.
Because the actuator base is supported on the spherical face of the valve housing via the rounded edge, tolerance-dictated skewed positions and assembly-dictated shifting of the actuator head can be compensated for. For sealing purposes, an O-ring is supported in an annular groove in the region of the actuator base. As viewed from the direction of the actuator head, the O-ring is located behind the rounded edge.
The structural group formed of the piezoelectric actuator unit and the coupling module forms a valve control unit of the fuel injection valve and serves to control a nozzle needle, which is located in an injector module of the fuel injection valve and cooperates with injection openings that lead to a combustion chamber of the engine.
In the installation of the known valve, the actuator base is prestressed by a spring sleeve, which surrounds the coupling module, with a force of approximately 700 N. Upon compensation for a tolerance-dictated skewed position and assembly-dictated shifting of the actuator head, a frictional moment occurs in the region of the rounded edge, which acts as a ball bearing. This frictional moment generates bending stresses, which can lead to damage, in the piezoelectric actuator unit.
To avoid leaks in the region of the O-ring seal, the regions of the actuator base that define the annular groove for the O-ring are located in the valve housing with a slight lateral play. The slight play disadvantageously means that the possible rotation of the actuator base is very slight, and as a result it may not be possible to compensate adequately for the incident tolerance-dictated rotations and assembly-dictated shifting of the actuator head.
Moreover, there is the problem in the known valve that the O-ring must be stretched greatly to be installed in the annular groove; on the one hand, this means increased effort in installation and on the other it can lead to increased rotation of the O-ring, and this rotation can disadvantageously cause leaks.